1. Field of the Invention
The present invention relates to a cantilever, a cantilever system including the cantilever, a scanning probe microscope including the system, a mass sensor apparatus, an elasticity measuring apparatus, and a manipulation apparatus. In addition, the present invention relates to a cantilever displacement measuring method of measuring a displacement of the cantilever, a cantilever oscillating method of oscillating the cantilever, and a cantilever deforming method of deforming the cantilever.
2. Description of the Related Art
In recent years, as nanotechnology progresses, sensors utilizing a cantilever are proposed, which require techniques of performing shape observation, mass, density, viscoelasticity, magnetic force, potential, current, and optical information measurement, processing, and manipulation. As one of apparatuses for realizing the above-mentioned requirement, there is known a scanning probe microscope (SPM). The scanning probe microscope is an apparatus capable of observing a very small region on a surface of various types of test samples including a metal, a semiconductor, a ceramic, a resin, a high polymer, a biomaterial, and an insulator, and hence observing a surface shape of the test sample and various physical properties thereof such as viscoelasticity at high resolution of an atomic level. Further, the scanning probe microscope can be used in various environments, e.g., in a vacuum, in a gas, in the air, in a liquid, or the like, and hence it is suitably used in a wide spectrum of fields.
In addition, the scanning probe microscope has various measurement modes corresponding to various objects to be measured, so it is necessary to select an optimal measurement mode every time of the measurement. As one of them, there is known an oscillation mode SPM in which a cantilever set in a cantilever holder is oscillated to perform measurement.
Examples of the oscillation mode SPM include a dynamic force mode microscope (DFM or a resonance mode measurement-atomic force microscope), in which a scanning is performed while controlling the distance between a probe and a test sample so that the oscillation amplitude of a resonated cantilever becomes constant, a viscoelastic AFM (VE-AFM or a micro viscoelasticity measurement-atomic force microscope), in which a test sample is oscillated as a small oscillation in a Z direction perpendicular to the surface of the test sample during an AFM operation, or a cantilever is oscillated as a small oscillation in the Z direction perpendicular to the surface of the test sample, to thereby apply a periodical force to the test sample while a deformation amplitude of the cantilever, a sine component, or a cosine component thereof is detected so as to measure a viscoelasticity distribution, and a lateral force modulation friction force microscope (LM-FFM), in which the test sample is oscillated as a lateral oscillation in the horizontal direction that is parallel to the surface of the test sample during the AFM operation, or the cantilever is oscillated as a lateral oscillation in the horizontal direction that is parallel to the surface of the test sample while a torsional oscillation amplitude of the cantilever is detected, to thereby measure a friction force distribution.
Here, in order to oscillate the cantilever, it is common to use a method of oscillating an oscillating source that is attached to a periphery of the cantilever (e.g., a cantilever holder) and transmitting the oscillation to the cantilever so that the cantilever is oscillated at a predetermined frequency and amplitude (see Japanese Patent No. 3222410). Alternatively, another method is also adopted in some quarters, in which a magnetic member is attached to the cantilever in place of the oscillating source, and a magnetic field generated by the magnetic member is utilized for oscillating the cantilever.
However, the conventional measuring method according to the oscillation mode SPM has yet the following problems.
Specifically, in the method of utilizing the oscillating source for oscillating the cantilever, the oscillation of the oscillating source also propagates to peripheral structural members other than the cantilever so as to cause the peripheral structural members to be oscillated. Therefore, the oscillation characteristic of the cantilever is affected to be different from ideal oscillation state. As a result, it is difficult to identify resonance characteristics of the cantilever correctly, and it is difficult to set correctly an oscillation frequency, an oscillation amplitude, and a phase oscillation characteristic. Therefore, it is difficult to measure the test sample with high accuracy.
On the other hand, the method of utilizing the magnetic member for oscillating the cantilever has some inconveniences as described below.
First, because it is necessary to attach the magnetic member to the cantilever, a material of the cantilever is limited. Therefore, it is impossible to select an optimal cantilever from various cantilevers having various oscillation characteristics, which causes an inconvenience that the selection range is narrowed.
In addition, because a mechanism for generating a magnetic field is necessary as a structure of the apparatus, the mechanism leads to an increase in cost. In addition, heat is generated when the magnetic field is generated. Therefore, an influence of the heat causes generation of a drift, which may cause a decrease in resolution. Further, because it is necessary to install a mechanism for generating the magnetic field, the apparatus structure becomes a large scale, which deteriorates the entire stiffness, leading to a decrease in resolution and a decrease in operation speed. In addition, the installation of the mechanism for generating the magnetic field may suffer a limitation of space such as a decrease in the measurement region, a limitation of the movable range, or a disturbance of parallel use of an optical microscope because upper and lower spaces of the cantilever are occupied by the mechanism.
Here, oscillating the cantilever means deforming repeatedly and periodically the cantilever. Noting this deformation, generally, the cantilever does not deform by itself but is deformed by an external factor. In other words, the cantilever is bent and deformed when a repulsive force or an attractive force is exerted by the test sample, or when a micro-substance or the like is adhered. However, recently, there is often a demand for a self-active deformation of the cantilever in order to perform more multidirectional observation or measurement. Conventional cantilevers cannot meet such a demand.